This invention relates to propulsion arrangements for fluid-borne vehicles having a configuration which is generally symmetric about the vehicle axis.
Conventional propulsion systems for axisymmetric fluid-borne vehicles include internally powered, shaft-driven propeller-type drive systems and strut-mounted pod systems. Conventional propeller and shaft drive systems are susceptible to damage during shallow draft operations and damage from large ingested foreign materials. From a maintenance standpoint such conventional drive systems are cumbersome and require access from places within the vehicle, resulting in major disruption within the engine room because of the size of the components involved.
The Lehmann U.S. Pat. No. 3,182,623 discloses a jet propulsion unit for a submarine which comprises a tail section attached to the pressure hull of the submarine and having a plurality of pairs of intake ducts extending inwardly from opposite sides near the forward end of the tail section to a common central duct, each of the intake ducts having an impeller surrounded by a drive motor.
The Kim U.S. Pat. No. 5,045,004 describes a turbo-hydro duct propulsion arrangement producing a high pressure water jet to propel an underwater vehicle. The water jet has symmetrical exit nozzles. The Patent to Garis, U.S. Pat. No. 5,078,628, shows a marine propulsor for use on submarine-type vessels in which the entire propulsion system is housed outside of the hull and has an electric motor which drives a single set of blades within the housing. The Cho U.S. Pat. No. 5,702,273 describes a similar propulsion arrangement for underwater vehicles.
According to the Meng U.S. Pat. No. 5,333,444, an electromagnetic thruster for marine vehicles produces a water jet by the interaction of an intensified magnetic field and an intensified electric field. A plurality of such thrusters is symmetrically mounted around the stern of a vessel with intake openings uniformly disposed around the forward end of the periphery of the unit to cause the boundary layer passing along the surface of the vessel to be drawn into the intake. Each of the thrusters is partially embedded within a section at the stern of the vessel and control surfaces are nested around the modules so that they do not interfere with the inflow or are affected by the module outflow.